1. Field of the Invention
The present invention relates to supplying line to a subsea well. More particularly, the present invention relates to operation of a subsea-mounted system to deliver pressure controlled grease at the subsea well location. Additionally, the present invention relates to a providing an efficient and constant supply of grease during line deployment.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98
Subsea production systems are used to explore, drill and harvest oil and gas field under the ocean floor. Subsea production systems sometimes require drilling of the wells from more than one location, and water and depth factors further determine the establishment of the oil and gas field. Thus, special equipment is required to develop subsea oil and gas fields. Equipment for subsea production systems are constructed with considerations for withstanding extreme conditions, being economically cost-effective, and safe guarding the environment. Even the activity of deploying this equipment requires specialized and expensive vessels. For example, diving devices and robotic devices are used for varying water depths. Maintenance for repair and intervention on the ocean floor are usually very economically costly. The locations are remote, the equipment itself is difficult to transport and to deploy, the delivery of building and maintenance resources spans large underwater distances, and the expense of intervention can risk economic failure of an entire subsea production system.
In subsea oil and gas production, electric line is used to carry a load and supply electricity to equipment in the subsea well. The electric line must be resilient enough to extend from a surface location to the subsea well and into the well. There are two types of electric line: smooth wire and braided wire. Smooth wire is the plain linear electric line dispensed from the surface location. Braided wire is twisted or coiled, increasing flexibility and resiliency in a subsea environment. Other types of lines, such as slickline, are smooth, and there are other types of braided lines. These lines may not have electric functions, although they may have other wireline functions.
It is important to maintain a sealed and protected environment for the integrity of the electrical line and transmission of electricity, accounting for the adverse conditions of being underwater, heave compensation, length of distance traveled from the surface, and variable pressure at ocean depths. For smooth wire, the sealed environment is established by friction-fit elastomeric seals at the subsea well location. FIG. 1 shows this prior art system for smooth wire. The water cannot pass into the well as the smooth wire 10 passes through the seal 12 and into the well 14. For braided wire, the friction-fit seals are not sufficient. Because the surface of braided wire is not smooth, there is no seal against the outer diameter of the wire and the inner diameter of the annular seal. Water and fluids can pass through the annular seal and into the well.
The typical system to maintain the sealed environment for braided wire is a grease tube device, as shown in FIG. 2. A grease tube 16 dispensed from the surface has an inner diameter to be slighter larger than the braided wire 18. In this manner, the braided wire 18 can pass through the grease tube 16, across a seal 20, and into the well 22. The outer surface of the braided wire 18 is not sealed against the seal 20 because of the un-smooth surface of the braided wire 18. To maintain the seal, grease 24 is pumped from the surface and through the grease tube 16, filling the annulus formed by the braided wire 18 and the seal 20. The viscosity of the grease 24 is cooperative with the un-sealed friction-fit relationship between the braided wire 18 and the seal 20. As such, the use of grease 24 is sufficient to provide a sealing means for the well 22.
In the past, various patents have been issued in the field of delivery of grease and lubricant to a subsea well. For example, U.S. Pat. No. 6,609,571, issued on Aug. 26, 2003 to Nice, teaches a remote subsea lubricator. The lubricator is used for inserting a wireline tool into a subsea well. The lubricator has an elongated tube having an axial passage formed therethrough for receiving the wireline tool. The remote subsea lubricator is lowered beneath the surface of the sea for connection to a subsea well. Contained within the lubricator is the wireline tool. Once connected to the subsea well, the wireline tool is released from the lubricator into the well. The lubricator enables the wireline tool to enter and exit the well without sea water entering the well.
U.S. Pat. No. 4,821,799, issued on Apr. 18, 1989 to Wong teaches a system for sealing around a wireline run into or pulled from wells. The system includes a grease control head with a line wiper mounted on the well head and a grease injection control system. The grease injection control system supplies grease continuously at a constant pressure for injection into the grease control head. The control system utilizes a piston pump to supply grease to a grease chamber in a pressurizing accumulator. The accumulator has another chamber connected to a remote pressure source, which is separated from the grease chamber by a moveable partition. Constant pressure from the remote source is transmitted through the moveable partition to grease in the grease chamber maintaining a constant pressure on grease injected into the grease control head. The sealing system is provided with a conduit to return injected grease pumped through the grease head to a waste grease reservoir for disposal. This conduit includes a valve which may be closed to aid in reestablishing a blown-out grease seal.
U.S. Pat. No. 4,227,543, issued on Oct. 14, 1980 to Williams, Jr. describes a ram-type blowout preventer for use in the drilling of onshore and offshore wells. The invention has a secondary plastic injection sealing means whereby, on failure of the conventional ram seal, a well closure may still be ensured for protection of human life, equipment and the environment.
U.S. Pat. No. 4,090,573, issued on May 23, 1978, teaches an apparatus and method for use during earth boring operations when a wireline instrument is positioned within the drill string while drilling fluid is circulated, such as during directional drilling. The apparatus includes a circulating head connected to the top of the drill string that is connected to the drilling fluid pump. A wireline sealing apparatus is connected to and extends partially into the inner passage of the circulating head. The wireline sealing apparatus is of the type that has a flow tube closely fitted about the wireline and in communication with grease supplied under high pressure. The grease provides a seal while the line is stationary and while moving. Consequently, after the wireline instrument reaches the bottom of the drill string, the wireline may be pulled upward while drilling fluid is being circulated to remove slack. The wireline instrument also may be lowered and retrieved while drilling fluid is being circulated.
U.S. Pat. No. 4,386,783, issued on Jun. 7, 1983 to Davis, teaches a packing nut which when retrofitted to or assembled into a stuffing box and hydraulically or manually actuated applies force to packing in the stuffing box, compressing the packing to seal on stationary wireline or pump rods or to wipe or seal on moving wireline or rods passing through a hole in a piston rod on which there is an operating piston in the packing nut body. The piston rod may be rotated to adjust its length for packing contact, and desired packing compression may be maintained by further rod rotation if pressured fluid is not available for hydraulic actuation. A connection for a remotely pressured fluid conduit is provided on the packing nut housing to deliver actuating fluid to the operating piston.
U.S. Pat. No. 4,428,421, issued on Jan. 31, 1984 to Rankin, describes a wireline apparatus and method having features that prevent the wireline from moving with respect to the drill string due to drill string movement or wave action on the drill rig. The apparatus includes a frame having a wireline pressure sealing device. Wireline is wrapped around the drum and reeved over a sheave which is mounted to the frame near the top of the wireline sealing device. A lift sub is secured to the top of the frame and enables the frame to be lifted by the rig elevators. The frame provides a linkage between the elevators and the drill string to lift the drill string.
U.S. Patent Publication No. 2008/026643, published on Oct. 30, 2008 to Skeels et al., describes a subsea intervention system. The system is directed to a device adapted to be positioned adjacent an end of a tool housing of a subsea lubricator, wherein the device includes a structural member that is adapted to be positioned adjacent an end of the tool housing, a non-metallic body coupled to the structural member and a sealing device that is adapted to sealingly engage a wireline extending through the sealing device. The present invention is also directed to a method which includes lowering an assembly toward a tool housing of a subsea lubricator positioned subsea using a wireline for the tool to support a weight of the assembly, wherein the assembly includes a wireline tool and a device including a structural member that is adapted to be positioned adjacent the end of a tool housing, a non-metallic body coupled to the structural member, and a sealing device that is adapted to sealingly engage a wireline extending through the sealing device.
U.S. Patent Publication No. 2002/0104662, published on Aug. 8, 2002 to Dallas, teaches a seal assembly for dual string coil tubing injection into a subterranean well, including a seal plate having first and second bores with annular seals for providing a high-pressure fluid seal around first and second coil tubing strings inserted through the respective bores. The seal plate is adapted to be connected directly to a wellhead, or a lubricator if a downhole tool is connected to either one, or both of the first and second coil tubing strings. The seal assembly further includes passages for supplying lubricant to the first and second annular seals to lubricate the respective seals while the respective first and second coil tubing strings are injected into and extracted from the wellhead.
Problems remain for maintaining the seal for braided wire. In particular, the top of the prior art grease tube has an elastomeric stopper to retain the grease 24 in the grease tube 16 as grease 24 is pulled through the seal 20 by the braided wire 18 in FIG. 2. To replace this grease 24 in the grease tube 16, grease 24 is pumped through the pressurized grease tube 16. The pumped grease 24 through the grease tube 16 also provides the pressure at maintain the seal into the well 22, even as some grease 24 enters the well 22. This grease pumping presents significant obstacles for dispensing the necessary electric line. The grease must be pumped long distances from the surface to the subsea location, and the pumping action is forced through extreme environmental conditions, including temperature variations. As the temperature drops underwater, the grease becomes more viscous and difficult to pump. Powerful equipment and significant energy sources are required at the surface to complete the pumping activity. As the depth of the subsea location increases, even more power is required to move so much grease through the grease tube. The requirement for extensive pumping equipment and energy resources to accomplish the pumping show that the prior art fails to address the needs of the industry.
It is an object of the present invention to provide a grease cartridge system to maintain a sealed well during deployment of electric line.
It is an object of the present invention to provide a method for delivering grease to a sealed well during deployment of electric line at variable pressure.
It is another object of the present invention to provide a method for delivering grease without pumping from a surface location.
It is still another object of the present invention to provide a system to supply grease to a sealed well from a subsea source.
It is an object of the present invention to provide a constant supply of grease during deployment of the electric line.
It is another object of the present invention to provide a removable and replaceable grease cartridge system at a subsea well.
It is still another object of the present invention to provide a method of grease recovery from deployment of the electric line.
It is another object of the present invention to provide a cost-efficient and energy-saving system for deployment of braided wire into a sealed subsea well.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.